The grass genera of the world
Habit, vegetative morphology. Perennial; caespitose. The flowering culms leafy (but tending to carry the racemes on specialised, 1-leafed culms). Culms about 10–50 cm high; herbaceous; unbranched above. Culm nodes glabrous. Culm internodes solid. Plants unarmed. Young shoots extravaginal, or intravaginal. Leaves not basally aggregated; non-auriculate. Leaf blades broad; pseudopetiolate; cross veined; persistent; rolled in bud. Ligule a fringed membrane; 0.5–1.2 mm long.
Reproductive organization. Plants monoecious with all the fertile spikelets unisexual; without hermaphrodite florets. The spikelets of sexually distinct forms on the same plant; female-only and male-only. The male and female-fertile spikelets mixed in the inflorescence (paired, male and female). The spikelets overtly heteromorphic. Not viviparous.
Inflorescence. Inflorescence a short raceme, terminal on a normal leafy or a special 1-leafed culm, borne horizontally beneath the blade of the bent subtending leaf. Spikelet-bearing axes persistent. Articles not appendaged; glabrous. Spikelets paired (male and female); not secund; pedicellate; not in distinct long-and-short combinations.
Female-sterile spikelets. Male spikelets with glumes reduced or lacking, having 3 stamens plus 3 staminodes and a sterile ovary with three stigmas. The male spikelets without glumes (or these vestigial); without proximal incomplete florets; 1 floreted. The lemmas awnless. Male florets 3 staminate, or 6 staminate (including the 3 staminodes). The staminal filaments free.
Female-fertile spikelets. Spikelets 9–11 mm long; not noticeably compressed; falling with the glumes. Rachilla terminated by a female-fertile floret.
Glumes two; more or less equal; long relative to the adjacent lemmas; hairless; awnless; non-carinate; similar (herbaceous, cuspidate). Lower glume 5–6 nerved. Upper glume 5–7 nerved. Spikelets with female-fertile florets only; without proximal incomplete florets.
Female-fertile florets 1. Lemmas similar in texture to the glumes (leathery); not becoming indurated; entire; blunt; awnless; hairless; glabrous; non-carinate; without a germination flap; 5–8 nerved. Palea present; relatively long; entire; awnless, without apical setae; not indurated; 2-nerved to several nerved; keel-less. Lodicules present; 3; free; fleshy; glabrous; toothed; not or scarcely vascularized. Stamens 0 (three staminodes). Styles fused (style base hairy). Stigmas 2.
Fruit, embryo and seedling. Fruit free from both lemma and palea; medium sized; compressed dorsiventrally. Hilum long-linear. Embryo small; not waisted. Endosperm hard; containing compound starch grains.
Seedling with a short mesocotyl; with a loose coleoptile. First seedling leaf without a lamina (two bladeless sheaths).
Abaxial leaf blade epidermis. Costal/intercostal zonation conspicuous. Papillae present. Intercostal papillae over-arching the stomata; several per cell. Long-cells markedly different in shape costally and intercostally; of similar wall thickness costally and intercostally. Mid-intercostal long-cells rectangular; having markedly sinuous walls. Microhairs present; panicoid-type. Stomata common. Subsidiaries triangular. Guard-cells overlapping to flush with the interstomatals. Intercostal short-cells common; in cork/silica-cell pairs; silicified. Intercostal silica bodies vertically elongated-nodular (?). Costal short-cells conspicuously in long rows. Costal silica bodies oryzoid.
Transverse section of leaf blade, physiology. C3; XyMS+. Mesophyll with non-radiate chlorenchyma; with arm cells; with fusoids. Leaf blade adaxially flat. Midrib having a conventional arc of bundles. Bulliforms present in discrete, regular adaxial groups; in simple fans (the groups wide). All the vascular bundles accompanied by sclerenchyma. Combined sclerenchyma girders present; forming figures. Sclerenchyma all associated with vascular bundles.
Cytology. Chromosome base number, x = 11.
Classification. Watson & Dallwitz (1994): Bambusoideae; Oryzodae; Olyreae. Soreng et al. (2015): Bambusoideae; Bambusodae; Olyreae; Olyrinae. 2 species (D. bicolor, D. tatianae).
Distribution, phytogeography, ecology. Panama.
Shade species. Forest.
We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, and classifications. See also Guidelines for using data taken from Web publications.
Cite this publication as: ‘Watson, L., Macfarlane, T.D., and Dallwitz, M.J. 1992 onwards. The grass genera of the world: descriptions, illustrations, identification, and information retrieval; including synonyms, morphology, anatomy, physiology, phytochemistry, cytology, classification, pathogens, world and local distribution, and references. Version: 11th December 2017. delta-intkey.com/grass’.